[PATCH 4.18 096/235] x86/mm/pti: Add an overflow check to pti_clone_pmds()

[Greg Kroah-Hartman]

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Joerg Roedel <jroedel@xxxxxxx>

[ Upstream commit 935232ce28dfabff1171e5a7113b2d865fa9ee63 ]

The addr counter will overflow if the last PMD of the address space is
cloned, resulting in an endless loop.

Check for that and bail out of the loop when it happens.

Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Pavel Machek <pavel@xxxxxx>
Cc: "H . Peter Anvin" <hpa@xxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Jiri Kosina <jkosina@xxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: David Laight <David.Laight@xxxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: Eduardo Valentin <eduval@xxxxxxxxxx>
Cc: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: aliguori@xxxxxxxxxx
Cc: daniel.gruss@xxxxxxxxxxxxxx
Cc: hughd@xxxxxxxxxx
Cc: keescook@xxxxxxxxxx
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Waiman Long <llong@xxxxxxxxxx>
Cc: "David H . Gutteridge" <dhgutteridge@xxxxxxxxxxxx>
Cc: joro@xxxxxxxxxx
Link: https://lkml.kernel.org/r/1531906876-13451-25-git-send-email-joro@xxxxxxxxxx
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/x86/mm/pti.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -306,6 +306,10 @@ pti_clone_pmds(unsigned long start, unsi
 		p4d_t *p4d;
 		pud_t *pud;
 
+		/* Overflow check */
+		if (addr < start)
+			break;
+
 		pgd = pgd_offset_k(addr);
 		if (WARN_ON(pgd_none(*pgd)))
 			return;